In some integrated circuits, e.g. IC memory card with self destruction capability, it is necessary to boost an available power supply voltage to provide a voltage substantially above the conventional 5 volts power supply to destroy the circuits within the IC memory card. The destroyed IC memory card then can not be used further by the illegal holder.
Review of conventional techniques of the charge pump may be found in the Background of the Invention of U.S. Pat. No. 5,392,205 ('205).
In '205, a novel regulated charge pump which finds its best application in a battery-based system is introduced. The '205 is hereinafter referred for all purposes of the prosecution of the instant invention.
However, due to the following reasons, the circuits disclosed in the '205 creates substantial noise on the N-well of the P-substrate on which the charge pump is implemented. During the charging phase, the 153 is ON which makes the node 73 to have value of Vss. During the pumping phase, the 154 is ON which makes node 73 to have value of Vbat. Therefore, as Vbat equals 5.4 volts and Vdd equals 5 volts, the voltage of the capacitor 80 is -0.4 volts. So the voltage of the node 72 varies between 5 and -0.4 volts, and that of the node 73 varies between 5.4 and 0 volts. And as Vbat equals 2.7 volts and Vdd equals 5 volts, the voltage of the capacitor 80 is 2.3 volts. So the voltage of the node 72 varies between 5 and 2.3 volts, and that of the node 73 varies between 2.7 and 0 volts. Due to the parasitic capacitance existing between the P-substrate and the N-well therein, substantial variation mentioned above creates noise over the N-well.
It is, therefore, the main object of the instant invention to provide a charge pump circuits with low noise on the well of the substrate on which the charge pump is embodied.